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 A225375 Odd numbers with exactly 2 distinct prime factors. 4
 15, 21, 33, 35, 39, 45, 51, 55, 57, 63, 65, 69, 75, 77, 85, 87, 91, 93, 95, 99, 111, 115, 117, 119, 123, 129, 133, 135, 141, 143, 145, 147, 153, 155, 159, 161, 171, 175, 177, 183, 185, 187, 189, 201, 203, 205, 207, 209, 213, 215, 217, 219, 221, 225, 235, 237 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers of the form p^i*q^j where p, q are distinct odd primes and i>=1, j>=1. Subset of A098905 (which contains in addition A046390 and numbers like 255255, 285285, 345345, 373065 etc.). LINKS Table of n, a(n) for n=1..56. MAPLE isA225375 := proc(n) RETURN( (n mod 2 = 1) and (A001221(n) = 2) ); end proc: for n from 1 to 840 do if isA225375(n) then printf("%d, ", n) ; end if; end do: MATHEMATICA Select[2 Range[200] + 1, PrimeNu[#] == 2&] (* Jean-François Alcover, Apr 04 2020 *) PROG (PARI) is_A046388(n)={ bittest(n, 0) & omega(n)==2 } \\ M. F. Hasler, Feb 13 2012 CROSSREFS Subsequence of A272592. A046388 is a subsequence. Cf. A046315, A046390, A046404, A024556, A056913. Different from A046388, A098905. Sequence in context: A185307 A061346 A098905 * A329229 A146166 A024556 Adjacent sequences: A225372 A225373 A225374 * A225376 A225377 A225378 KEYWORD nonn AUTHOR R. J. Mathar, Oct 13 2008 EXTENSIONS Entry created by N. J. A. Sloane, May 09 2013 in order to restore the original definition of A046388. STATUS approved

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Last modified September 18 23:40 EDT 2024. Contains 376002 sequences. (Running on oeis4.)